1. Field of the Invention
This invention relates in general to a coded signal reproducing device for a video tape recorder and particularly it is suitable for application to a PCM recorder wherein a coded audio signal is recorded and reproduced using a video tape recorder.
2. Description of the Prior Art
In a PCM recorder wherein an audio signal is subjected to PCM conversion, and then recorded and reproduced by VTR and demodulated to obtain the audio signal, the VTR will sometimes be set at variable speed reproducing modes for obtaining a heading signal contained in the recorded audio signal sources. For tape dubbing, also the VTR will sometimes be set to a high speed reproducing mode.
In such variable speed reproducing modes, if a reproduced PCM signal is demodulated, the pitch of the voice will be changed thus making it impossible to discriminate voice signals so the speed change ratio cannot be varied to a large extent. So as to avoid this inconvenience, a random access memory has been utilized for expanding the time base of a reproduced PCM signal into normal state by controlling the write and read clock frequencies so as to obtain the reproduced sound. According to this method, it is required that a longer time be utilized to read out the information from the RAM than was required in the writing operation which results in loss in information with respect to the reproduced information. The amount of information which must be received is reduced at a ratio corresponding to the time base expansion according to the playback speed ratio. Also, when the two rotational head type VTR is used at high speed reproducing mode such as during picture search modes, for example, as one of the rotational heads (A-head) scans across plural B-tracks recorded with another head (B-head) having a different azimuth with respect to the A-head, the RF output from the head will fall periodically and drop out becomes very noticeable. For such reproduced signals, the error-detecting and error-correcting operation in a PCM signal processor will not longer be assured, thus causing abnormal sound and clicks to be generated.